54 Scientific Proceedings, Royal Dublin Society. 



to the values of the units of length, time, and mass, belonging to 

 this which is a truly natural series of physical units. 



For such a purpose we must select phenomena that prevail 

 throughout the whole of Nature, and are not specially associated 

 with individual bodies. The first of Nature's quantities of abso- 

 lute magnitude to which I will invite attention is that remark- 

 able velocity of an absolute amount, independent of the units in 

 which it is measured, which connects all systematic electrostatic 

 units with the electromagnetic units of the same series. I shall 

 call this velocity Vj. If it were taken as our unit velocity we 

 should at one stroke have an immense simplification introduced 

 into our treatment of the whole range of electric phenomena, 

 and probably into our study of light and heat. 



Again Nature presents us with one particular coefficient of 

 gravitation, of an absolute amount independent of the units in 

 which it is measured, and which appears to extend to ponderable 

 matter of every description throughout the whole material uni- 

 verse. This coefficient I shall call Gi. If we were to take this 

 as our unit of coefficients of attraction, it is presumable that we 

 might thereby lay the foundation for detecting wherein lies the 

 connection which we cannot but suspect between this most won- 

 derful property common to all ponderable matter, and the other 

 phenomena of nature. 



And, finally, Nature presents us in the phenomenon of electro- 

 lysis, with a single definite quantity of electricity which is inde- 

 pendent of the particular bodies acted on. To make this clear 

 I shall express " Faraday's Law " in the following terms which, 

 as I shall show, will give it precision, viz. : — For each chemical 

 bond which is ruptured within an electrolyte, a certain quantity 

 of electricity traverses the electrolyte, which is the same in all 

 cases. This definite quantity of electricity I shaU call Ej. If we 

 make this our unit quantity of electricity, we shall probably have 

 made a very important step in our study of molecular phenomena. 



Hence we have very good reason to suppose that in Yj, G^, and 

 Ei, we have three of a series of systematic units that in an 

 eminent sense are the units of Nature, and stand in an intimate 

 relation with the work which goes on in her mighty laboratory. 



The approximate values of Vi and Gi are known, and I will 

 presently endeavour to evaluate E^. Yj has been variously de- 



